/Engine/Source/Runtime/Engine/Classes/Components/InstancedStaticMeshComponent.h
Get the translated space for instance transforms to be passed to the renderer. In the renderer data structures we only have floating point precision for instance transforms relative to their owning primitive. The primitive transform itself has double precision. Some ISM that are authored in world space need to adjust the local space to keep instance transforms within precision limits.
virtual FVector GetTranslatedInstanceSpaceOrigin() const